In a significant advancement for nanoscale spectroscopy, the scientists have introduced a novel approach to enhance the time resolution of tip-enhanced Raman (TER) spectroscopy. By utilizing a mechanically chopped laser beam as the excitation source, they have successfully pushed the technique’s temporal resolution towards the (sub)millisecond scale, without compromising the spectral quality achieved with traditional continuous wave (cw) excitation. This advancement addresses a long-standing challenge in the field, as previous attempts to improve time resolution using picosecond or femtosecond laser pulses often resulted in a trade-off with spectral resolution.
The study focused on analyzing a (sub)monolayer of thiophenol adsorbed on an Au(111) surface, with the scientists investigating the stability of the TER signal as a function of time and laser power. The results were promising, demonstrating that TER spectra obtained with chopped excitation exhibited similar stability, sensitivity, spectral resolution, peak position, peak width, and signal-to-noise ratio (SNR) as those recorded using cw excitation.
Moreover, the proposed methodology considered an increased tolerance of pulsed laser power at the tip/sample junction and the adsorbed molecules before degradation occurred. This work opens up exciting possibilities for performing ambient TER measurements with millisecond-scale temporal resolution, while maintaining spectral resolution and SNR comparable to those achieved with cw excitation. Notably, the approach does not require any modifications to the standard detection system of the TER set-up, making it an accessible and practical solution for researchers in the field.